Lacy Mandigo, 18, of Statesville, N.C., auditioned with Dusty Springfield’s “Son of a Preacher Man.” A big growl on the final note prompted a chair turn from Christina Aguilera and earned Lacy a spot on the show. Her audition was montaged with two others, so we saw only a moment of it. But Lacy said she had dreamed that Christina would turn at the last moment, just like it happened.